This invention is directed towards an improvement in a liquid propellant gun system. More particularly it is directed towards the liquid propellant used with such a system. It is directed toward the hydrocarbon used with other components of the liquid propellant.
In a liquid propellant gun, hereinafter referred to as LPG, system a liquid supplies energy to drive the projectile forward. This is in contrast to the solid, e.g., gunpowder, or nitrocellulose-based and other smokeless propellants used in a conventional gun. The liquid used in LPG is a combination of several components. Generally a liquid hydrocarbon and nitric acid are the components. Thus the combination can be referred to as bipropellant. Just prior to ignition, the bipropellant is an emulsion.
A LPG system generally operates as follows. The projectile is inserted in the barrel of a gun and its fit is such that it forms a liquid tight seal. A bolt and injection nozzle are located behind the projectile when it is in position. Nitric acid and hydrocarbon are simultaneously mixed and injected into the chamber, i.e., the space between projectile and the bolt. After the chamber is filled with the bipropellant, the bolt moves forward and seals the injection nozzle. A spark ignition device is used to generate a spark which ignites the bipropellant. The spark device can be located in the bolt or elsewhere.
Hydrocarbons such as n-octane have been tried and found not totally satisfactory. More recently a mixture of endo and exo tetrahydrodimethyldicyclopentadienes has been used. A mixture of the foregoing is often referred to as a TH-dimer. However, the TH-dimer has deficiencies. For example, TH-dimer upon mixing with aqueous nitric acid undergoes nitration at ambient temperature with evolution of considerable heat.
Surprisingly applicants have discovered that if, for example, the hydrocarbon used contains a majority of the exo form of several hydrocarbons the foregoing premature nitration problem does not exist. Also, other types of hydrocarbons were also found to be usable.
A method for preparing tetrahydrodicyclopentadienes is disclosed in U.S. Pat. No. 3,381,046, Apr. 30, 1968 and JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Vol. 82, 1960, pages 4645-4651. Methods of preparation for the other hydrocarbons found suitable are known to those skilled in the art.